This invention relates to a natch configuration for a multi-part mold, such that a common natch part is used for both male and female natches as used in mating mold parts.
In the fabrication of molds for use in molding articles from vitreous enamel, china, and the like, many difficulties are experienced with natches which are commonly used with such molds, particularly with natches for production molds which are fabricated from plaster of paris. An important function of the natches is to maintain the precise alignment of mating mold parts, to produce a perfect seam on the molded product. One difficulty is that the natches become loose within the plaster of paris mold long before the mold is otherwise worn out; and the mold must then be discarded prematurely resulting in increased mold expense. Many natch configurations are two-part natches consisting of mating male and female parts. Such two-part natches are inherently more expensive, since the purchase and stocking of two separate parts is required. In many of the available natches, the mating alignment surfaces are complementary partial spherical surfaces, one convex and one concave. One difficulty with natches of this type, which are fabricated from metal, is that these complementary mating surfaces tend to deform resulting in poor alignment. Another difficulty with this type of natch is that the two natch parts do not stay together in precise mating relationship during fabrication of the mold parts; and the natches tend to float or move away from each other during the fabrication process. When this occurs, of course, the natches cannot perform their alignment function for the completed mold parts. Apart from the above mentioned difficulties with natches having spherical mating surfaces, even when the natches are properly positioned relative to the mold parts, the alignment of these spherical surfaces is imprecise so that ultimate alignment of the mold parts is not as precise as it might be. In other words, the mating male and female spherical surfaces fit together loosely in many instances. For all commercial natches having spherical mating surfaces, some material such as clay, vaseline or other form of temporary stickem must be used to hold the natches together during the mold fabrication and which can be readily removed after the mold is made. This involves two additional processing steps, namely, the placing of the stickem and the removal of the stickem.
A principal object of this invention is to provide a new and improved natch which overcomes the deficiencies and disadvantages of prior art natches as discussed above.
Another important object of this invention is to provide a new and improved natch which is a single unit natch, functioning as both the male and female mating natch members.
A further object of this invention is to provide a new and improved natch which is suitable for use with both large molds, such as molds for sanitary ware, and small molds such as molds for artware and fine china.
Still another object of this invention is to provide a new and improved natch which holds the mold parts together in perfect alignment for a perfect seam fit, and which maintains the parting lines for the mold parts through many casts.
A still further object of this invention is to provide a new and improved natch which will stay rigidly in place within the mold part throughout the life of the mold.
Another object of this invention is to provide a new and improved natch which is economic to manufacture.
These objects are accomplished in a natch for plaster molds which comprises a unitary, generally cylindrical body having a cylindrical coupling recess at one end and a reduced diameter cylindrical coupling boss at the other end. The inner diameter of the coupling recess and the outer diameter of the coupling boss correspond to each other, whereby the coupling recess of one natch will receive the coupling boss of another natch with a friction fit. The coupling boss, together with the adjacent portion of the body, defines an annular alignment shoulder facing the other end of the body; and the one end of the body has an external annular alignment flange defining an alignment end face. The natch body has means defining a radially projecting retainer flange disposed between, and spaced axially from, the alignment end face and the alignment shoulder. The retainer flange means has a noncircular periphery.
The novel features and the advantages of the invention, as well as additional objects thereof, will be understood more fully from the following description when read in connection with the accompanying drawings.